Tue September 10, 2019 4:00 pm
Harald Hess: From evaporative cooling and BEC in hydrogen to microscopy innovation in biology
Location:Harvard Jefferson 250
Harold Hess, Janelia Research Campus
Ten Minute Talk:"TBD" by
Lawrence Cheuk
The first search to observe BEC in spin-polarized hydrogen began in the early 1980’s and employed confinement in cryogenic cells. Progress was halted abruptly with the recognition that three-body recombination blocked these approaches to BEC: at higher temperatures, volume recombination was prohibitive; at lower temperatures, recombination on the cryogenic surface was prohibitive. Switching to the high-field seeking states and employing a pure magnetic trap made surface-free confinement possible but required a new cooling method. We demonstrated that by lowering the depth of the trap, the more energetic atoms would escape and as the gas re-thermalized its temperature would drop [1]. Subsequently we switched to rf evaporation, which greatly improved the cooling efficiency. The process turned out to be extremely well suited to the alkali metal atoms where it enabled the first observation of BEC in a gas. Several years later, it enabled us to observe of BEC in hydrogen.
The lessons learned as a postdoc in the BEC challenge, both technical and philosophical, proved to be a good base for a career in numerous other physics topics. I will describe a personal path that lead to low temperature scanning tunneling electron microscopy of vortices and a series of other scanned probe microscopes for studying nanoscale physics at Bell Labs. A focus on the high throughput, large scale imaging challenges of semiconductor industry provided a new perspective to imaging and later on offered the liberating horizons of unemployment. Together with another jobless ex-Bell Labs colleague, we conceived of a new super-resolution optical microscope [2]. This led to employment and a variety of 3D volume microscopy challenges and new instrumentation for biology, some of which are inspired by research in atomic physics.
[1] H. Hess, Phys. Rev B 34, 5, 3476 (1986).
[2] E. Betzig et al, Science 313, 1642 (2006).